Structurally Strengthened Battery Enclosure

The disclosure relates to rechargeable energy storage systems (“RESS”) and more particularly relates to battery enclosures within rechargeable energy storage systems.

Rechargeable energy storage systems, including lithium-ion and related batteries, are increasingly being used in a variety of fields as a way to more efficiently generate, store, and distribute electrical power. In automotive applications, rechargeable energy storage systems are being used as a way to supplement, in the case of hybrid electric vehicles (HEVs), or supplant, in the case of purely electric vehicles (EVs), i.e., battery electric vehicles (BEVs), conventional internal combustion engines. The ability to passively store energy from stationary and portable sources, as well as from recaptured kinetic energy provided by the vehicle and its components, makes batteries ideal to serve as part of a propulsion system for cars, trucks, buses, motorcycles and related vehicular platforms. In the present context, a cell is a single electrochemical unit, whereas a battery is made up of one or more cells joined in series, parallel or both, depending on desired output voltage and capacity.

Temperature is one of the most significant factors impacting both the performance and life of a battery. Environmental temperatures (such as those encountered during protracted periods of inactivity in cold or hot environments, or due to extended periods of operation and concomitant heat generation on hot days) or abuse conditions (such as the rapid charge/discharge, or internal/external shorts caused by the physical deformation, penetration, or manufacturing defects of the cells) can negatively impact the ability of the battery to operate correctly, and in severe cases can destroy the battery entirely. Side effects of prolonged exposure to high temperature may include premature aging and accelerated capacity fade, both of which are undesirable.

Excess heat can be provided by an internal short circuit in a battery cell. An onset temperature is that temperature at which an exothermic reaction occurs. The heat required to maintain such an exothermic reaction is known as the heat of reaction, while a heat source that exceeds the onset temperature and maintains the heat of reaction is a thermal event. Such thermal events, if left uncontrolled, could potentially lead to a more accelerated heat generation condition, referred to herein as thermal runaway, a condition where (once initiated) the cooling mechanism is incapable of returning one or more of the battery components to a safe operating temperature. In the present context, a thermal runaway is a function of the self-heating rate of the exothermic reaction and the temperature, and the time of the reaction is a function of the rate of degradation and the mass of active components taking part in such reaction. Of particular concern is the possibility for excess heating of, and concomitant damage to, a battery cell, group, pack or related member being used as a source of propulsive power.

Accordingly, it is desirable to provide battery enclosures and methods for improving thermal performance of battery enclosures. Further, it is desirable to structurally strengthen battery enclosures. Other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing introduction.

In an embodiment, a method for improving thermal performance of a battery enclosure includes forming the battery enclosure with a bottom wall and a side wall, wherein the side wall includes a bottom section, a middle section, and a top section; reducing a thickness of the middle section and top section to form a bottom step between the bottom section and the middle section; forming a top step from the top section; and locating internal battery components within the battery enclosure. In the method, the top step has a first thickness, the bottom step has a second thickness, and the middle section has a third thickness; the first thickness is greater than the third thickness; and the second thickness is greater than the third thickness.

In certain embodiments of the method, forming the top step includes folding the top section to create a fold and inserting a wedge into the fold.

In certain embodiments of the method, forming the top step further includes welding together the fold and the wedge.

In certain embodiments of the method, forming the top step includes placing a sleeve around the top section and welding the sleeve to the top section to form the top step.

In certain embodiments of the method, the first thickness is at least 1.5 times greater than the third thickness.

In certain embodiments of the method, the second thickness is at least 1.5 times greater than the third thickness.

In certain embodiments of the method, the top step surrounds the top section of the battery enclosure, and the bottom step surrounds the bottom section of the battery enclosure.

In certain embodiments of the method, improving thermal performance includes placing a cold plate below the bottom section of the battery enclosure.

In certain embodiments of the method, improving thermal performance further includes transferring heat from the bottom section to the cold plate.

In certain embodiments of the method, the battery enclosure is a first battery enclosure, and the method further includes placing a second battery enclosure adjacent to the first battery enclosure, wherein a gap is defined between the first battery enclosure and the second battery enclosure; and placing a barrier within the gap between the first battery enclosure and the second battery enclosure.

In certain embodiments, the method further includes configuring the middle section of the first battery enclosure to expand freely into the gap.

In certain embodiments of the method, is comprised of a thermal barrier.

In another embodiment, a battery enclosure is provided and includes a bottom wall; a side wall including a bottom section, a middle section, and a top section; a bottom step; and a top step. In the battery enclosure, the top step has a first thickness, the bottom step has a second thickness and the middle section has a third thickness; the first thickness is greater than the third thickness and the second thickness is greater than the third thickness.

In certain embodiments of the battery enclosure, the top step and bottom step are configured to reduce rupture risk of the battery enclosure.

In certain embodiments of the battery enclosure, the bottom step is configured to transfer heat to a cold plate.

In certain embodiments of the battery enclosure, the bottom step completely surrounds the bottom section of the battery enclosure.

In certain embodiments of the battery enclosure, the top step completely surrounds the top section of the battery enclosure.

In certain embodiments of the battery enclosure, the first thickness is at least 1.5 times greater than the third thickness.

In certain embodiments of the battery enclosure, the second thickness is at least 1.5 times greater than the third thickness.

1 5 In another embodiment, a vehicle is provided and includes an electric motor configured to provide motive torque; and a battery system operatively connected to the electric motor and operable to provide electrical power to the electric motor, wherein the battery system includes a battery enclosure surrounding an internal space and including a bottom wall and a side wall, wherein the side wall includes a bottom section, a middle section, and a top section; a bottom step is formed at a bottom interface between the bottom section and the middle section; a top step is formed at a top interface between the top section and the middle section; the top section is at least 1.5 times thicker than the middle section; the bottom section is at least.times thicker than the middle section; the bottom step is configured to transfer heat; the bottom step and top step are configured to structurally strengthen the battery enclosure; the middle section is configured to allow swelling of internal battery components by expanding to increase a volume of the internal space.

The following detailed description is merely exemplary in nature and is not intended to limit the application and uses of embodiments herein. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding introduction, summary or the following detailed description.

Embodiments of the present disclosure may be described herein in terms of functional and/or logical block components and various processing steps. Connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure.

For purposes of the present description, unless specifically disclaimed, use of the singular includes the plural and vice versa, the terms “and” and “or” shall be both conjunctive and disjunctive, and the words “including”, “containing”, “comprising”, “having”, and the like shall mean “including without limitation”. Moreover, words of approximation such as “about”, “almost”, “substantially”, “generally”, “approximately”, etc., may be used herein in the sense of “at, near, or nearly at”, or “within 0-5% of”, or “within acceptable manufacturing tolerances”, or logical combinations thereof. As used herein, a component that is “configured to” perform a specified function is capable of performing the specified function without alteration, rather than merely having potential to perform the specified function after further modification. In other words, the described hardware, when expressly configured to perform the specified function, is specifically selected, created, implemented, utilized, programmed, and/or designed for the purpose of performing the specified function.

Embodiments herein may provide for improved battery cell materials and/or improved battery cell fabrication methods. More specifically, embodiments herein provide a high strength can or enclosure design for a large energy battery cell to improve cell safety during cell thermal runaway. For example, embodiments herein provide a stepped enclosure design that provides for a lower cell mass/higher cell energy ratio. Further, embodiments herein provide a stepped enclosure design that provides for increased structural strength at corners of the battery enclosure.

A large energy cell, i.e., greater than 1 kWh, holds promise for significantly reducing battery pack costs. The cost of cell mechanical components, such as the cap plate, remains similar on a per-piece basis, but the cost per kWh decreases with higher cell energy, resulting in lower overall cell costs. Additionally, larger cell energy allows for fewer cells in a pack, reducing the number of components, overall pack cost, and mass.

However, large energy cells pose higher risks of cell rupture during thermal runaway due to the increased energy and gas release. Embodiments herein address this higher risk by providing a stepped case or enclosure design that strengthens the weak points at enclosure corners, effectively reducing the risks of cell rupture without significantly increasing cell mass or reducing cell energy. The stepped case design may also reduce internal cell swelling forces by setting an initial cell-to-cell space or void providing for enclosure expansion at selected sections. Furthermore, embodiments herein may improve thermal performance by increasing the heat conduction or transfer area.

In certain embodiments, the enclosure design includes varied side wall thicknesses with locally thicker side walls at and near enclosure corners to strengthen the enclosure without dramatically increasing the cell mass or decreasing cell energy.

In certain embodiments, the enclosure design introduces a gap between battery cells in the battery module, which allows each cell to expand and reduces the internal cell swelling force.

In certain embodiments, the enclosure design provides a larger thermal conduction area that facilitates heat conduction to a cold plate and improves thermal performance of the enclosure.

In certain embodiments, the enclosure design can be introduced during prismatic case manufacturing processing and may include folding and welding or extrusion or deep drawing. For deep drawing, a thicker can wall section near the bottom surface can be established during an ironing phase of the can deep drawing process. Further a top section may be formed by folding and then welding to increase the wall thickness.

In certain embodiments, methods for forming the enclosure include welded or adhering a metal plate or sleeve onto the box-like enclosure. In such embodiments, the metal plate or sleeve could be a different material from the can base material, such as copper.

Embodiments herein are applicable to various cell chemistries and are applicable to both electrode stack and wound jelly roll designs.

Certain embodiments provide a cell array including a thermal barrier material between cells and gaps between the thermal barrier material and portions of the cells. This design allows cells to expand without constraint to reduce the internal cell swelling force at end of life. Alternatively, a soft foam can be used to fill the gap without constraining cell expansion.

In certain embodiments, a stepped case design is used for a large energy cell to improve thermal performance. The stepped case is locally thicker near the cooling surfaces to facilitate heat conduction. Cooling locations may include top walls, side walls, and bottom walls.

Certain embodiments provide for improved cell thermal performance with lower cell maximum temperature during charging and discharging. Certain embodiments provide for improved cell life because of lower cell maximum operation temperatures. Certain embodiments provide for improved abuse performance.

Embodiments of the present disclosure offer advantages over the existing art, though it is understood that other embodiments may offer different advantages, not all advantages are necessarily discussed herein, and no particular advantage is required for all embodiments.

100 200 1 FIG. Referring to the drawings, wherein like reference numbers correspond to like or similar components wherever possible throughout the several figures, an electric vehiclehaving a rechargeable energy storage system (“RESS”)including a plurality of battery cells in a battery assembly, is shown in. The term “battery” used alone herein may refer to a battery module, battery cell or cell stack. The term “battery pack” used alone may refer to a battery and the battery enclosure system the battery is housed within.

1 FIG. 100 100 200 illustrates the electric vehicleas an automobile, such as any one of a number of different types of automobiles, such as, for example, a sedan, a wagon, a truck, sport utility vehicle (SUV), or the like. In certain implementations, the vehiclemay comprise a motorcycle or other land-based vehicle, such as a rail locomotive, or a non-land-based vehicle such as aircraft, spacecraft, watercraft, and so on, and/or one or more other types of mobile platforms (e.g., a robot and/or another mobile platform). In yet other implementations, the RESSmay instead be part of and/or coupled to any number of other types of platforms and/or other systems, moving or non-moving, such as a building, infrastructure, secondary use, home power, non-automotive, and/or other platforms and/or other systems.

100 112 200 118 114 118 114 112 118 200 100 100 116 118 200 118 The illustrated electric vehicleincludes a vehicle chassis. The RESSincludes a battery moduleand is provided with a battery trayfor supporting the battery module. The battery traymay attach to the vehicle chassisto secure the battery modulein the RESSto the electric vehicle. The electric vehiclemay also include a battery disconnect unit, which is connected to the battery moduleof the RESS. In exemplary embodiments, battery moduleis an assembly of battery cells.

2 FIG. 1 FIG. 2 FIG. 700 118 700 is a schematic perspective view of a battery cellof the battery moduleof. Specifically,illustrates a prismatic battery cell.

700 720 725 720 720 720 720 720 724 720 720 850 The prismatic battery cellis illustrated as including an outer case or enclosurethat surrounds and defines an internal spacewithin the enclosure. An exemplary outer enclosuremay be conductive. For example, the outer enclosuremay be metallic. In certain embodiments, the enclosureis aluminum. The illustrated outer enclosureis a rectangular polyhedron formed from four side walls, though the enclosuremay be of any suitable shape. The enclosureincludes a bottom wall.

720 860 860 720 860 860 The outer enclosuremay be formed with an open top end, which is covered or closed by a cap. In certain embodiments, the capmay be part of the enclosure. In certain embodiments, the capis conductive. For example, the capmay be metallic, such as aluminum or aluminum alloy.

700 735 720 735 860 As shown, the battery cellmay include tabs or terminals, which may be in electrical connection with the battery cell components within the outer enclosure. In certain embodiments, each terminalis insulated from the cap.

700 740 740 700 720 725 In certain embodiments, the battery cellincludes an electrode assembly. As shown, the electrode assemblyis illustrated with dashed lines, indicating the electrode assemblyas a component of the prismatic battery cellthat is internal to the hard outer enclosure, i.e., located within the internal space.

3 FIG. 2 FIG. 3 FIG. 700 700 726 is a cross-sectional schematic of the battery cellof. In, internal components of the battery cellare generally indicated by reference number.

3 FIG. 724 720 810 820 830 810 820 815 815 820 830 825 825 As shown in, each of the side wallsof the outer enclosureis formed with a bottom section, a middle section, and a top section. The bottom sectionjoins the middle sectionat an interfaceor step. The middle sectionjoins the top sectionat an interfaceor step.

3 FIG. 810 724 819 725 810 724 818 810 724 811 819 818 As shown in, the bottom sectionof each side wallhas an inner surfacedefining the internal space. Further, the bottom sectionof each side wallhas an outer surface. As shown, the bottom sectionof each side wallhas a thicknessextending between the inner surfaceand the outer surface.

810 815 805 810 805 815 810 812 As further shown, the bottom sectionextends from interfaceto a bottom surface. The bottom sectionterminates at the bottom surfaceand at the interface. The bottom sectionhas a vertical height.

3 FIG. 830 724 839 725 830 724 838 830 724 831 839 838 As shown in, the top sectionof each side wallhas an inner surfacedefining the internal space. Further, the top sectionof each side wallhas an outer surface. As shown, the top sectionof each side wallhas a thicknessextending between the inner surfaceand the outer surface.

830 825 835 830 835 825 830 832 As further shown, the top sectionextends from interfaceto a top surface. The top sectionterminates at the top surfaceand at the interface. The top sectionhas a vertical height.

3 FIG. 820 724 829 725 820 724 828 820 724 821 829 828 In, the middle sectionof each side wallhas an inner surfacedefining the internal space. Further, the middle sectionof each side wallhas an outer surface. As shown, the middle sectionof each side wallhas a thicknessextending between the inner surfaceand the outer surface.

820 815 825 820 815 825 820 822 As further shown, the middle sectionextends from interfaceto interface. The middle sectionterminates at the interfaceand at the interface. The middle sectionhas a vertical height.

811 821 811 821 821 821 821 821 821 821 821 821 821 821 821 In certain embodiments, the bottom thicknessis greater than the middle thickness. For example, bottom thicknessmay be at least 1.1 times the middle thickness, such as at least 1.2 times the middle thickness, at least 1.3 times the middle thickness, at least 1.4 times the middle thickness, at least 1.5 times the middle thickness, at least 1.6 times the middle thickness, at least 1.7 times the middle thickness, at least 1.8 times the middle thickness, at least 1.9 times the middle thickness, at least 2 times the middle thickness, at least 2.25 times the middle thickness, or at least 2.5 times the middle thickness.

811 821 821 821 821 821 821 821 821 821 821 821 821 In certain embodiments, bottom thicknessmay be at most 1.2 times the middle thickness, such as at most 1.3 times the middle thickness, at most 1.4 times the middle thickness, at most 1.5 times the middle thickness, at most 1.6 times the middle thickness, at most 1.7 times the middle thickness, at most 1.8 times the middle thickness, at most 1.9 times the middle thickness, at most 2 times the middle thickness, at most 2.25 times the middle thickness, at most 2.5 times the middle thickness, or at most 3 times the middle thickness.

831 821 831 821 821 821 821 821 821 821 821 821 821 821 821 In certain embodiments, the top thicknessis greater than the middle thickness.. For example, top thicknessmay be at least 1.1 times the middle thickness, such as at least 1.2 times the middle thickness, at least 1.3 times the middle thickness, at least 1.4 times the middle thickness, at least 1.5 times the middle thickness, at least 1.6 times the middle thickness, at least 1.7 times the middle thickness, at least 1.8 times the middle thickness, at least 1.9 times the middle thickness, at least 2 times the middle thickness, at least 2.25 times the middle thickness, or at least 2.5 times the middle thickness.

831 821 821 821 821 821 821 821 821 821 821 821 821 In certain embodiments, top thicknessmay be at most 1.2 times the middle thickness, such as at most 1.3 times the middle thickness, at most 1.4 times the middle thickness, at most 1.5 times the middle thickness, at most 1.6 times the middle thickness, at most 1.7 times the middle thickness, at most 1.8 times the middle thickness, at most 1.9 times the middle thickness, at most 2 times the middle thickness, at most 2.25 times the middle thickness, at most 2.5 times the middle thickness, or at most 3 times the middle thickness.

811 831 811 831 831 831 831 831 831 831 831 831 831 811 831 831 831 831 831 831 831 831 831 831 In certain embodiments, bottom thicknessand top thicknessare equal. In certain embodiments, bottom thicknessis at least 0.75 times the top thickness, such as at least 0.8 times the top thickness, at least 0.85 times the top thickness, at least 0.9 times the top thickness, at least 0.95 times the top thickness, at least 1.05 times the top thickness, at least 1.1 times the top thickness, at least 1.15 times the top thickness, at least 1.2 times the top thickness, or at least 1.25 times the top thickness. In certain embodiments, bottom thicknessis at most 0.75 times the top thickness, such as at most 0.8 times the top thickness, at most 0.85 times the top thickness, at most 0.9 times the top thickness, at most 0.95 times the top thickness, at most 1.05 times the top thickness, at most 1.1 times the top thickness, at most 1.15 times the top thickness, at most 1.2 times the top thickness, or at most 1.25 times the top thickness.

812 822 812 822 822 822 822 822 822 822 822 822 In certain embodiments, the bottom heightis less than the middle height. For example, bottom heightmay be at least 0.1 times the middle height, such as at least 0.2 times the middle height, at least 0.3 times the middle height, at least 0.4 times the middle height, at least 0.5 times the middle height, at least 0.6 times the middle height, at least 0.7 times the middle height, at least 0.8 times the middle height, or at least 0.9 times the middle height.

812 822 822 822 822 822 822 822 822 822 In certain embodiments, bottom heightmay be at most 0.1 times the middle height, such as at most 0.2 times the middle height, at most 0.3 times the middle height, at most 0.4 times the middle height, at most 0.5 times the middle height, at most 0.6 times the middle height, at most 0.7 times the middle height, at most 0.8 times the middle height, or at most 0.9 times the middle height.

832 822 832 822 822 822 822 822 822 822 822 822 In certain embodiments, the top heightis less than the middle height. For example, top heightmay be at least 0.1 times the middle height, such as at least 0.2 times the middle height, at least 0.3 times the middle height, at least 0.4 times the middle height, at least 0.5 times the middle height, at least 0.6 times the middle height, at least 0.7 times the middle height, at least 0.8 times the middle height, or at least 0.9 times the middle height.

832 822 822 822 822 822 822 822 822 822 In certain embodiments, top heightmay be at most 0.1 times the middle height, such as at most 0.2 times the middle height, at most 0.3 times the middle height, at most 0.4 times the middle height, at most 0.5 times the middle height, at most 0.6 times the middle height, at most 0.7 times the middle height, at most 0.8 times the middle height, or at most 0.9 times the middle height.

812 832 812 832 832 832 832 832 832 832 832 832 832 812 832 832 832 832 832 832 832 832 832 832 In certain embodiments, bottom heightand top heightare equal. In certain embodiments, bottom heightis at least 0.75 times the top height, such as at least 0.8 times the top height, at least 0.85 times the top height, at least 0.9 times the top height, at least 0.95 times the top height, at least 1.05 times the top height, at least 1.1 times the top height, at least 1.15 times the top height, at least 1.2 times the top height, or at least 1.25 times the top height. In certain embodiments, bottom heightis at most 0.75 times the top height, such as at most 0.8 times the top height, at most 0.85 times the top height, at most 0.9 times the top height, at most 0.95 times the top height, at most 1.05 times the top height, at most 1.1 times the top height, at most 1.15 times the top height, at most 1.2 times the top height, or at most 1.25 times the top height.

3 FIG. 816 815 818 828 816 805 816 811 821 As shown in, a bottom shoulder or bottom step surfaceis located at the interfaceand interconnects the bottom outer surfaceand middle outer surface. The bottom step surfacemay be substantially horizontal and/or substantially parallel to the bottom surface. The bottom step surfacemay have a horizontal length equal to the difference of bottom thicknessand middle thickness.

3 FIG. 826 825 838 828 826 835 826 831 821 As shown in, a top shoulder or top step surfaceis located at the interfaceand interconnects the top outer surfaceand middle outer surface. The top step surfacemay be substantially horizontal and/or substantially parallel to the top surface. The top step surfacemay have a horizontal length equal to the difference of top thicknessand middle thickness.

3 FIG. 850 859 725 850 858 850 852 859 858 In, the bottom wallhas an inner surfacedefining the internal space. Further, the bottom wallhas an outer surface. As shown, the bottom wallhas a vertical thicknessextending between the inner surfaceand the outer surface.

3 FIG. 860 869 725 860 868 860 862 869 868 In, the top caphas an inner surfacedefining the internal space. Further, the top caphas an outer surface. As shown, the top caphas a vertical thicknessextending between the inner surfaceand the outer surface.

852 862 852 862 862 862 862 862 862 862 862 862 862 852 862 862 862 862 862 862 862 862 862 862 In certain embodiments, vertical thicknessand vertical thicknessare equal. In certain embodiments, bottom vertical thicknessis at least 0.75 times the top vertical thickness, such as at least 0.8 times the top vertical thickness, at least 0.85 times the top vertical thickness, at least 0.9 times the top vertical thickness, at least 0.95 times the top vertical thickness, at least 1.05 times the top vertical thickness, at least 1.1 times the top vertical thickness, at least 1.15 times the top vertical thickness, at least 1.2 times the top vertical thickness, or at least 1.25 times the top vertical thickness. In certain embodiments, bottom vertical thicknessis at most 0.75 times the top vertical thickness, such as at most 0.8 times the top vertical thickness, at most 0.85 times the top vertical thickness, at most 0.9 times the top vertical thickness, at most 0.95 times the top vertical thickness, at most 1.05 times the top vertical thickness, at most 1.1 times the top vertical thickness, at most 1.15 times the top vertical thickness, at most 1.2 times the top vertical thickness, or at most 1.25 times the top vertical thickness.

4 FIG. 3 FIG. 5 11 FIGS.- 3 FIG. 1000 720 is a flow chart illustrating a methodfor improving thermal performance of a battery enclosure, such as battery enclosureof.are cross-sectional views, similar to, that illustrate stages of fabrication of the battery enclosure and assembly.

4 5 FIGS.and 5 FIG. 4000 4010 720 810 820 830 724 811 720 850 850 720 Cross-referencing, methodmay include, at operation, forming an initial battery enclosure. As shown in, in the initial stage the bottom section, middle section, and top sectionof the side wallshave a substantially constant thickness, which may be equal to thickness. In certain embodiments, the initial battery enclosureincludes the bottom wall, though in other embodiments the bottom wallmay be later formed. In certain embodiments, forming the initial battery enclosureincludes blanking and drawing a metal into the desired box-like shape.

4 6 FIGS.and 4000 4020 816 815 810 820 820 830 821 Cross-referencing, methodmay include, at operation, forming a bottom step. Specifically, bottom shoulder or bottom step surfaceis formed at the interfaceof bottom sectionand middle section. As shown, the middle sectionand top sectionare reduced in thickness, such as to thickness.

4020 820 830 724 810 811 821 In certain embodiments, operationincludes an ironing process to reduce the thickness of the middle sectionsand top sectionsof side walls. During this process, the bottom sectionis not fully ironed and remains at the thicknessgreater than thickness.

4 FIG. 4000 4030 As shown in, methodmay continue at operationwith forming a top step.

7 FIG. 3 FIG. 7 FIG. 3 FIG. 830 881 880 830 826 880 882 830 835 As shown in, the top step may be formed by folding the top section. Specifically, the top endand a folded portionof the top sectionis folded downward to form the top step(shown in). As shown in, the folded portionends at a foldin the top sectionthat forms the top surface(also shown in).

4030 885 880 830 880 830 Operationmay further include locating a weld materialbetween the folded portionand the remaining unfolded top section. Then, a welding process is performed to join the folded portionto the remaining unfolded top section.

8 FIG. 8 FIG. 3 FIG. 4030 4030 890 835 830 895 891 890 825 820 830 891 826 4030 890 724 4030 890 724 890 720 890 720 890 illustrates an alternative process for forming the top step at operation. In, operationincludes sliding a sleeveover the top endof top section, as indicated by arrow. A bottom edgeof the sleeveextends to and may define the interfacebetween the middle sectionand the top section. Thus, bottom edgemay form the top step(shown in). Operationmay include welding the sleeveto the side walls. In other embodiments, operationmay include adhering the sleeveto the side walls, such as with glue. In certain embodiments, the sleeveis the same material as the enclosure. Alternatively, the sleevemay be a different material than the enclosure. For example, the sleevemay aluminum, copper, or other suitable material.

4 FIG. 9 FIG. 4000 4040 720 In, methodmay continue at operationwith locating internal battery components within the enclosure, as shown in.

4 FIG. 10 FIG. 4000 4050 720 860 In, methodmay continue at operationwith sealing the battery enclosurewith the top cap, as shown in.

4 10 FIGS.and 4000 4060 810 724 720 950 950 4060 700 950 Cross-referencing, methodmay further include, at operation, contacting the bottom sectionof the side wallsof the enclosurewith a heat transfer plate, or cold plate. For example, operationmay include mounting batteryto the cold plate.

4 10 FIGS.and 4000 4070 720 701 950 805 810 724 810 805 810 950 Still cross-referencing, methodmay further include, at operation, transferring heat from the battery enclosure(and battery) to the heat transfer platethrough the bottom surfaceof the bottom sectionof the side walls. With the increased thickness of the bottom section, the heat transfer area between the bottom surfaceof the bottom sectionand the heat transfer plateis increased and provided for increased heat transfer, i.e., a faster rate of heat transfer.

4 11 FIGS.and 4000 4080 960 900 701 960 701 702 960 Cross-referencing, methodmay further include, at operation, placing a barrierin a gapadjacent to the battery. In certain embodiments, the barrieris a thermal barrier providing for heat insulation between batteriesand. For example, the barriermay be formed from an insulative thermoset material.

4 11 FIGS.and 4000 4090 702 701 701 702 700 4080 702 950 701 702 701 900 Cross-referencing, methodmay further include, at operation, placing a next batteryadjacent to a battery. Each batteryandis formed according to the method for forming battery. Operationmay include mounting batteryto the cold plateat a located next to battery. After locating batterynext to battery, gapis defined therebetween.

960 900 920 820 724 701 702 920 701 702 820 920 In the embodiment shown, the barrierdoes not completely fill the gap. Rather, voidsremain between the middle sectionsof the side wallsof each batteryand. The presence of the voidsallows for each batteryandto expand at the respective middle sectionwithout constraint to reduce cell swelling force within the batteries at the end of life. Alternatively, a soft foam material may be used to fill the voids.

810 950 4070 After locating all batteries as desired, method may continue with transferring heat from the respective bottom sectionsto the heat transfer plate, such as during charging and discharging of the batteries, at operation.

720 830 724 831 826 724 720 724 724 3 FIG. 3 FIG. In certain embodiments, the enclosureis rectangular. In such embodiments, the top sectionof each of the four side wallsmay have the same thicknessshown in. In such embodiments, the top shoulder or top step surfaceis annular, i.e., extends around all four side wallsof the enclosure. Thus, for such embodiments,provides a same cross-sectional view across first and third opposite side walls, and across second and fourth opposite side walls.

720 826 724 830 831 826 724 830 In other embodiments, the enclosureis rectangular but does not have an annular top step surface. Specifically, first and third opposite side wallsare formed with top sectionhaving thicknessand a top step surface, but second and fourth opposite side wallsdo not have top sectionswith an increased thickness.

12 FIG. 2 FIG. 12 FIG. 700 724 830 724 833 821 820 724 is a cross-sectional schematic of the battery cellof, taken across second and fourth opposite side walls. As shown in, the top sectionof second and fourth opposite side wallsmay be formed with a thicknessthat is equal to or substantially equal to the thicknessof the middle sectionof each side wall.

3 12 FIGS.and 720 724 830 831 826 724 830 833 826 Cross-referencing, an enclosuremay have first and third opposite side wallsformed with top sectionshaving thicknessand a top step surface, and have second and fourth opposite side wallsformed with top sectionshaving thicknessand no top step surface.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.